This invention pertains to electrical switches of a type having snap action, and in particular to an electrical switching mechanism which offers the snap action and dual set points.
There have been temperature or pressure actuated switches or switching mechanisms which use belleville-type springs for resisting actuation, in order to give the same an operating, snap action. Exemplary thereof is U.S. Pat. No. 4,853,504, issued to Hazime Tanaka et al, on Aug. 1, 1989, for a Triple Action Pressure Switch. This patented switch employs snap disc assemblies to open and close resiliently supported contacts. Such switches, it is found, are susceptible to faulty operation and functioning due to vibration, shock and the like. Another reference of interest is U.S. Pat. No. 5,004,873, issued on Apr. 2, 1991, to Robert H. Schnut, for Plural Set Point Pressure Responsive Switching Apparatus Utilizing a Single Pressure Sensing Driver. In this apparatus, a belleville snap spring is employed to actuate and deactuate microswitch-type elements. The snap spring translates an actuator which, in turn, actuates the aforesaid elements, and the latter elements, in turn, open and close electrical circuits. Such sequential functioning invites failures, and requires considerable maintenance.
In U.S. Pat. No. 3,876,845, issued on Apr. 8, 1975, to Donald L. Griffith and Lawrence A. Dunham, for Pressure and Temperature Actuated Switches Utilizing Belleville springs, is disclosed a belleville spring-actuated switch which is not susceptible to malfunctioning due to shock or vibration. Too, the switch comprises fixed contacts, and an actuator which carries a shunting disc for direct make or break contact with the fixed contacts. What has been needed is an electrical switching mechanism, similar to the aforecited U.S. Pat. No. 3,876,845, which, however, will offer dual setpoints.